Diamonds and other gemstones are often marked for purposes of identification, security and tracking. Unique marks, symbols, logos or bar codes are often used to provide a particular gemstone, such as, for example, a diamond, with a unique characteristic, so that the marked stone can be identified and distinguished from other gemstones. Many techniques, such as laser etching and ion beam marking, have been proposed for imprinting the unique indicia on the gemstone.
Typically, the mark can be seen using a jeweler's loop or an ordinary microscope. A problem with known marking techniques is that the marks produced can be seen and altered by unauthorized persons, and thus, rendered unusable as a unique identifying mark. Accordingly, there is a need for a marking method that imprints a unique identifying mark that is difficult to detect and alter.